But how do we actually make water drinkable?

The fact that we are lucky enough to have sufficient quantities of natural water in underground water tables doesn't mean that it is ready for us to drink, because it may be contaminated by industrial, agricultural or domestic pollution. Where such contamination exists, the soil is no longer capable of fulfilling its natural regulatory and purification role, and we must treat the water to make it safe for human consumption.

This is the process that water goes through before it arrives in your glass. If we follow the route taken by a single drop of water, you'll soon see that this is a long journey, and one with many potential pitfalls along the way.

Stage 1: Our drop of water is drawn from a lake, a spring, a river or an underground water table. This is called Abstraction.

Stage 2: To begin with, this drop of water must pass through a simple mesh to remove the largest solid debris. It is then filtered through a series of progressively finer filters. These processes are referred to as Screening and Fine Screening.

Stage 3: A flocculent is then added to the water. This process causes any remaining solids to fall as flocs to the bottom of a huge settling tank. These steps are called Flocculation and Decantation.

Stage 4: Our drop of water must now face another test. It must find its way through a bed of fine sand, whose job is to remove particles so small that they are invisible to the naked eye. This is Sand filtration.

Stage 5: Our journey is still far from over! Our drop of water is now disinfected using a gas - Ozone - which will kill any bacteria and viruses it contains. This stage is called Ozonization.

Stage 6: Now, it has to pass through particles of activated carbon, which retains the very smallest particles, such as pesticides. This is the Activated Carbon Filtration phase.

Stage 7: Chlorine is now added to prevent bacteria from growing in the water as it passes through the supply pipes. This is Chlorination.

Stage 8: Our drop of water is now approaching the end of its journey, stored in high-level reservoirs or water supply tanks. From here, it will travel through the frost-protected underground pipeline network and into your tap.

So the next time you pour yourself a glass of water, take a shower or clean your teeth, remember this little drop of water and its very long journey!